Datapages, Inc.Print this page

Structural Style and Deformation History of Assam & Assam Arakan Basin, India: from Integrated Seismic Study

Akhtar, Mohammad S.1; Chakrabarti, Sumit 1; Singh, Ram Krishna 1; RoyMoulik, Sujit 1; Bhattacharya, Jayant 1; Singh, Harvinderjit 1
1 Basin Research Group, ONGC Ltd.India, Dehradun, Uttarakhand, India.

Assam Shelf located in Northeastern part of India has an extent of around 40,000 sq. Km. of area and belongs to the northeastern prolongation of the Indian Peninsular Shield, bounded in the north-west by the Eastern Himalayan Fold Belt and in the southeast by Naga-Patkai fold belt. Tectonically Assam-Arakan basin has been defined as a poly - history basin that evolved synchronous with the other East-Coast basins of India, concomitant with the rifting and subsequent drifting of the Indian Plate from Eastern Gondwanaland. The basin was initiated in an extensional phase and later modified by different episodes of compressional phase. Super-imposition of compressional phase on extensional regime modified the earlier extensional structures that indicate the poliphase / poli-history nature of the basin. About 7000m of sediments ranging in age between Cretaceous to Recent are expected to be present in the deepest part of basin.

For the last fifty years of exploration in the basin, a lot of geo-scientific data has been generated. Structural style and Deformation history of Assam Shelf has been an imperative need with the available datasets. In this endeavor efforts have been made to interpret seismic data of thirty-one 3-D volumes and 500 2-D seismic lines, sixty and more exploration wells and their integration with stratigraphic sections has enabled an understanding of 3-D geometry, spatial organization, genesis, and evolution of folds and faults leading to conceptualization, characteristics and evolution of the Structural Style of Assam Arakan Basin. Interpretations suggest that two major longitudinal high angle normal fault systems trending NE-SW and E-W have been identified in addition to the three inverted extensional faults. The transverse system of faults is the result of a youngest episode of compressive movement. The E-W and NE-SW longitudinal faults and the associated structures acted as major areas of entrapment of hydrocarbons. Inter play of extensional, compressive and lateral movement clearly explains the hydrocarbon accumulation pattern in the area. The purpose of this paper is to document an example of the structural patterns resulting from interacting normal and inverted extensional faults, and to illustrate the process of iterative seismic interpretation and structural modelling in a complexly deformed basin, based on the interpretation of a 2-D and 3-D seismic data set.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009